The present invention relates to molded articles, for example, hollow plastic balls. In our U.K Patent Specification 1 119 176 we disclose an apparatus for molding hollow plastic articles such as balls. These balls may be used for various leisure activities but one particular usage is in children's playpen areas.
These playpen areas will be filled with balls, and children will leap around and swim through the sea of balls. What often happens then is that balls get stood or jumped on and this reduces their life. The problem is to know which balls to replace.
The present invention provides a particularly convenient method of date or batch recording for use on molded hollow articles such as balls.
Accordingly the invention provides a hollow molded article such as a ball in which the wall surface comprises at least two adjacent regions whose shapes are determined by corresponding adjacent parts of a mold cavity,
The mold cavity parts being adjustable in position relative to one another and each having a shaping so that the molded article carries corresponding shapings whose relative positions indicate a batch or time of manufacture.
By the term shaping we mean a protuberance, indentation, or other marking which will be visible in the finished article in distinction from the intended general overall shape of the article.
In one form of the invention the air venting plug of a molding apparatus comprises a shaping in the form of markings corresponding approximately to a clock face, and includes an adjustable pin whose head defines a shaping and which can be inserted in one of a number of different holes in the mold face of the air venting plug. The corresponding shapings on the molded article, i.e. the clock face, and an indentation corresponding to the position of the pin head can then be used as an indication of the year of manufacture.
Often the air venting plug in a molding apparatus forms a small hemispherical segment of the blow molding cavity. In another form of the invention therefore, the air venting plug forms a minor hemispherical segment of the mold cavity and includes markings corresponding approximately to a clockface, and a permanent mark such as a pinhead sized indentation is provided as the shaping in an adjacent part of the mold cavity. Adjustment of the air venting plug by rotation changes the relative position between the pinhead sized shaping and the clock face shaping, so that in the molded article a different time, for example a different month of manufacture is indicated.
In a preferred form of the invention these two aspects are combined to provide indications of both year and month of manufacture.